Variable pulley transmissions comprising a pair of interconnected pulleys mounted on generally parallel shafts with each pulley having at least one of its flanges movable with respect to other flange to change the drive ratio therebetween are well known in the art. For many applications, the pulleys are interconnected by a rubber or other elastomer V-belt. However, for automotive drive applications elastomeric V-belts are not suitable because they are not generally able to handle the torque requirements.
A power transmission belt manufactured by superimposing a plurality of metal bands on one another in a "nested fashion" and providing thereon a plurality of generally V-shaped metal load blocks with angled edges to engage the pulley flanges, has been suggested in van Doorne et al, U.S. Pat. No. 3,720,113. A belt so manufactured is expensive and must be manufactured with close tolerance to properly function.
Chain-belts comprising a plurality of interleaved links joined by pivot means with one or more generally trapezoidal or V-shaped metal load blocks thereon have also been suggested in the co-pending application of Cole et al, U.S. Ser. No. 130,772, filed Mar. 17, 1980, now U.S. Pat. No. 4,313,730. These belts can be manufactured for much less cost than the van Doorne et al belts. However, significant noise levels at frequencies which may be objectionable to the human ear can be generated when the load block of the chain-belt successively engages the pulleys, as will be described. Also, the load may not be shared by all load blocks because of the chordal action of the belt and the pulleys, resulting in an uneven load distribution on the chain.